JPS58165500

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DESCRIPTION JPS58165500
[0001]
The present invention relates to an improvement of a diaphragm for an electroacoustic
transducer. Conventionally, an electro-acoustic transducer, for example, a diaphragm for a
speaker, is often made of a pulp paper diaphragm made of paper pulp fibers and formed by
heating and pressing, but this type of diaphragm has a small density in view of its characteristics.
Also, it has an advantage that the internal loss (tan δ) is appropriate, but because the Young's
modulus of the paper is extremely small, the rigidity of the diaphragm is not sufficient and it is
difficult to increase the high frequency reproduction limit frequency. It requires complicated
processes such as process, papermaking process, drying process, press process with mold, etc.
Also, entanglement between fibers at the time of papermaking, variation inevitably occurs in
press conditions etc., diaphragm having uniform acoustic characteristics Difficult to provide. On
the other hand, metal diaphragms utilizing high Young's modulus of metal are also put to
practical use, but the conversion efficiency is reduced due to the large density and the internal
loss is extremely small. It is difficult to provide a speaker with such frequency characteristics and
low distortion, and is currently used only for reproduction of a relatively small frequency band,
such as a relatively small tweeter. Furthermore, in recent years, diaphragms using a
thermoplastic resin or a thermosetting resin have been devised and put to practical use. For
example, a diaphragm made of bo-repropylene is relatively lightweight and has a large internal
loss, and an advantage that it can be easily formed by vacuum molding etc after forming it into a
film shape, and a large amount and uniform diaphragm can be provided. However, it has a
drawback that the high frequency band can not be made sufficiently high because the rigidity
(that is, the Young's modulus of polypropylene) does not have a satisfactory value. There is also a
diaphragm made of a synthetic resin mixed with graphite powder and mica powder as a filler to
increase the Young's modulus, but the increase in density is larger than that of the Young's
modulus, and furthermore, the inside of the synthetic resin There was a lack of loss, P. Therefore,
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in the present invention, by combining an organic filler: 1 :: and an inorganic filler into a
thermoplastic resin or a thermosetting resin in combination, it is possible to minimize the
decrease in internal loss and the increase in density. And an extremely large increase in Young's
modulus, hereinafter polypropylene is an organic filler, crystalline cellulose powder as an organic
filler, an inorganic filler, mica powder, natural graphite powder, titanium dioxide, mixed powder
of mica powder and natural graphite An embodiment using the above will be described in detail.
[Example 1] Polypropylene pellets obtained by mixing 15 wt% of mica powder having an average
particle diameter of 10 μm and 7 wt% of crystalline cellulose powder having an average particle
diameter of 40 μm which have been subjected to 7-rank cupping treatment The film was
formed.
Example 2 A polypropylene fiber in which 15 wt% of natural graphite powder having an average
particle diameter of 10 μm and 15 wt% of crystalline cellulose powder having an average
particle diameter of 40 μm were mixed, and a left was formed into a 0.5 fi thick film by injection
extrusion. [Example 3] '1 titanium dioxide having an average particle size of 1 oμm: 1 knee;'
(Ti02) Polypropylene pellets mixed with 16 wt% of crystalline cellulose powder and 16 wt% of an
average particle size of 40 pm are injection extruded. A 0.5 thick film was formed. Example 4
Injection-extrusion of polypropylene pellets mixed with 10 wt% of mica powder having an
average particle size of 10 μm, 15 wt% of natural graphite powder having an average particle
size of 10 μm and 1 Q wt% of crystalline cellulose having an average particle size of 40 μm. It
was molded into a film of 0.5 wm thickness by molding. Then, the films molded according to the
above-mentioned Example 1 to Example 4 are cut into a size of 1.5 cm × 5.5 cm, and the
density, Young's modulus and tan δ are measured and compared with the conventional
diaphragm material. It shows in the next table. As apparent from this table, the diaphragm
according to the present invention has a remarkable increase in Young's modulus as compared
with polypropylene, while the decrease in density and tan δ values is small. Considering this
cause, it is presumed that mixing a mixture of mica powder, natural graphite, titanium dioxide,
squid powder and natural graph eye 1 has made it possible. . Next, the films obtained in the
above Examples 1 to 4 are vacuum molded to obtain a cone-shaped diaphragm having an
effective vibration radius 22α, and this and a diaphragm having a diaphragm of the same
diameter vacuum-molded a polypropylene film. The characteristics are the diaphragms formed
with the films of FIGS. 3 and 4, and i is the frequency characteristic of the speaker provided with
the diaphragm formed with the polypropylene film. As is apparent from the figure, the
loudspeaker using the diaphragm of the present invention has a significantly increased high
frequency reproduction limit frequency, which enables superior wideband reproduction. In the
conventional polypropylene diaphragm panel, a dip has occurred around 4001H2. This is
because reverse resonance occurs at this frequency, but in the diaphragm of the present
invention, as the rigidity increases, the reverse frequency increases and the band decreases. Since
it is easy to suppress this reverse resonance because the internal loss is large, it seems that a dip
which is extremely clear like the conventional polypropylene diaphragm does not occur.
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As described above, the present invention is a thermoplastic resin comprising G mixed with an
organic filler and an inorganic filler. 9 B, sex □. It is possible to provide a speaker having a wide
reproduction frequency band and a flat frequency characteristic by increasing the Young's
modulus which is a defect of the synthetic resin without losing the advantage of the synthetic
resin as much as possible. Although the present invention of the present application is a
combination of a relatively low density polypropylene having a large tan δ among synthetic
resins and a low density crystalline cellulose powder as an organic filler, the best effect is
revealed by the combination, The present invention can be applied to thermoplastic resins such
as polyethylene as a synthetic resin, thermosetting resins such as phenol resin, melamine resin,
area resin, etc., and organic filler and 1 for example manila hemp powder, sawdust powder, and
inorganic filler for graphite. Etc.-Powders with relatively large Young's modulus can be applied.
[0002]
Brief description of the drawings
[0003]
The 1-a to 1-d are respectively frequency characteristics of the speaker equipped with the
diaphragm of the embodiment of the present invention: 1 'and the speaker equipped with a poly
1.
--- → 1 distribution temporary (l-1t) also I-, f figure procedure amendment (♂) May 7, 1984
Showa 561 patent application No. 191630 No. 2, name of the invention Vibration for electroacoustic transducer Board 3, Name of person making corrections (027) Representative of Onkyo
Co., Ltd., 5 Takeshi, Agent Address 〒 572 Osaka Prefecture Neyagawa City Nisshincho,
Nisshincho, No. 1 5, Date of correction instruction. Fig. 1-d is correct.
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